
Title 



..XI.. 

.'R s^ 



Imprint. 



18 — <IT872-a mm 



LABORATORY NOTES. 






•■\ 



SANITARY CHEMISTRY 



tV 



J r-1 j 



AND 



WATER ANALYSIS. 



Copyright, 1896, 
ELLEN H. RICHARDS. l/lM 



-■^ / 



A 



\ 



V 






LABORATORY NOTES ON SANITARY CHEMISTRY. 



[Prepared for the use of students in the Laboratory of Sanitary Chemistry of the Massacliusetts Institute 

of Technology. Not published.] 

The application of chemistry to problems of public health or ^en- 
eral sanitation is of comparatively recent date, and its importance can 
hardly be overrated from the present standpoint of the relation between 
health and the condition of air, water, and food materials as regards 
the action of the lower forms of life. Soil and food are the hotbeds 
in which these lower forms of life are propagated and from which they 
are carried by water and air as well as by actual contact. Sanitary 
biology is concerned with the organisms themselves; sanitary chemistry 
with the detection and interpretation of the changes which they cause 
in the materials in which they grow, and with the production of certain 
substances inimical to health. 

In these notes are illustrated the more common changes which are 
now known to be caused by these organisms. In order to interpret 
correctly the results obtained, it is necessary to know the normal com- 
position of the materials in question. To determine this often involves 
analytical processes not strictly included under the head of sanitary 
tests, namely, the determination of total solids, ash, etc., and certain 
changes of sanitary significance not due to the lower forms of life, such 
as the vitiation of air by the burning of lights or the breathing of human 
beings. Sanitary chemistry may also properly include the examination 
of articles of food for the presence of adulterants or poisons. 

It is evident that any classification of topics is only temporary and 
tentative in the present state of knowledge. Water analysis and air 
analysis are each treated in a separate section. In the former the 
products of bacterial action are to be most carefully studied and 
accurately determined, in order that the deductions from the results 
may be of value. Soil analysis has been fully described in works on 
agricultural chemistry (see Bibliography, page 28), and is therefore 
omitted. Food analysis is treated on the broad lines above indicated. 
A few typical substances only will be considered, and the methods of 
examination given will be such as to elucidate the scientific aspect 
rather than technical detail of the subject. Both on account of its 
importance as a food stuff and on account of its availability for the 
tests, MILK has been chosen as a type of animal food. This class 




includes meats and meat products, meat tablets, peptones, and other 
prepared animal foods. The same methods of examination may be 
applied to the analysis of fertilizers. 

The analysis of milk includes the determination of specific gravity, 
water or total solids, ash, fat, nitrogen, sugar, together with the separa- 
tion of casein and albumen, the determination of the products of pu- 
trefaction and fermentation, namely, ammonia and acidity, also the de- 
tection of |jreservatives and coloring matters. 

Wheat is taken as a type of vegetable food. This class includes 
macaroni, gluten, bread, beans, bananas, etc. Determinations are also 
made of water or total solids, ash, fat, nitrogen, starch, cellulose, and the 
products of peptonization and saccharification. 

The results of fermentation are illustrated by the determination of 
alcohol in beer, wine, meat extracts, patent medicines and "temperance 
drinks," flavoring essences, etc. 

The determination of the specific gravity and "extract" is also 
sometimes desirable. 

The nature and composition of butter and other animal fats, of 
olive and cottonseed oil, with tests for the identification of each, are 
also briefly considered. 

Condiments, spices, tea, and coffee are largely identified by mi- 
croscopic tests, but adulterations of these, as of most common grocer- 
ies, affect the health less than the pocket. Text-books on food adul- 
terations furnish sufficient information on these points. (See Biblio- 
graphy, page 28.) 

MILK ANALYSIS. 

General Stateme?its. — Milk is an emulsion of fat globules with 
casein and other albuminoids, mineral matters probably in combination, 
sugar and water. 

Dr. Vieth gives for the year 1890 the average of 22,670 samples 
and for eleven years the average of 120,540 samples, as follows: 



Specific gravity 
Total solids . 
Solids not fat 
Fat 



Average, 1890 



1.0322 


12.84 


9.10 


3-74 



Average of eleven years. 



12.90 


8.80 


4.10 



3 

The solids not fat are composed of — 

Milk sugar, 4.91 

Proteids, 3.27 

Mineral matter or ash, .70 



8.88 



An examination of milk as regards its healthfulness usually consists 
in determining what changes, if any, have taken place in its constituents 
due to the growth of microorganisms, for which it affords a most inviting 
culture medium. These changes are termed fermentations. The two 
most common are the acid and the alkaline. 

Acid Fermentation. — Milk sugar yields lactic acid under the 
influence of a class of organisms of which bacillus aadi ladici is one. 
The extent to which this change has taken place is shown by the test 
for acidity. 

Alkaline Fermentation. — Albumen and casein are decomposed 
with the formation of ammonia and other intermediate nitrogenous 
products, some of them of a poisonous character, as is shown by the 
prevalence of cholera infantum when such decomposed milk is used, 
and by cases of poisoning by ice cream, etc. The fat becomes in time 
rancid, perhaps by butyric fermentation, but this change takes place, 
as a rule, more slowly, and is not as common as the others. 

Alcoholic Fermentation. — The production of koumiss is an 
instance of an artificially incited change. There are various other 
occasional fermentations which cause a slimy appearance or a bitter 
taste or the production of butyric acid. The student is referred to 
the various journals for accounts of these. The United States Depart- 
ment of Agriculture has recently published Bulletin No. 25, on Dairy 
Bacteriology^ by H. W. Conn. 

The examination of milk for the detection of adulteration is con- 
fined to certain physical tests, and to the determination of water, fat, 
sugar, and ash, and the detection of harmful preservatives. In all 
manipulations with milk the importance of thorough and fiequent mix- 
ing, not shaking, cannot be too strongly emphasized; this is best accom. 
plished by pouring it from one vessel to another. The apparatus used 
in containing and measuring milk should be thoroughly washed out as 
soon as possible. 



PHYSICAL TESTS. 

Specific Gravity. — This is taken in the usual manner by a hydrom- 
eter or by the Westphal balance. The temperature should not vary 
more than two degrees from 15° C. A reading of the lactometer, a 
standard often used, and dependent upon average specific gravity, is 
also to be taken at the same time. 

Fat. — This is estimated by Feser's lactoscope, the modus operandi 
of which is given with that instrument. It is based upon the opacity 
of the milk. Another instrument of like principle is the pioscope of 
Professor Heeren (^Repit f. Anal. Chem., 188 1, p. 247), which consists 
of an ebonite disk with a raised rim ; a few drops of milk are brought 
upon it, the painted glass cover placed over it, and the color of the milk 
matched with one of those on the cover. 

Creatn. — The creamometer, an elongated test tube with graduations 
near the top, is filled to the zero mark with the milk, and allowed to 
stand twenty-four hours, after which the percentage of cream is read off. 
The rapidity with which the cream rises indicates whether sodium car- 
bonate has been added, its action being to retard the rise of cream. 
Should the cream separate very quickly and the milk be blue, the in- 
dication is that water has been added or that the milk is of poor quality. 
In the municipal laboratory at Amsterdam a few drops of a strong solu- 
tion of methyl violet are added to render the reading sharper, as it 
does not dissolve appreciably in the cream. Cream contains the most 
of the fat of milk, with a small proportion of the other constituents. 
One thousand and ten samples of cream gave an average of 48.3 per 
cent. fat. Skimmed milk, from centrifugal separators, yields from 0.2 to 
0.4 per cent. fat. If convenient, a microscopical examination should be 
made ; this will show the fat present as an infinite number of minute 
globules of various sizes, there being two or three million per cubic 
millimeter. 

CHEMICAL TESTS. 

Reaction. — Normal milk gives the amphioteric reaction, /. e.., turns 
delicate litmus both red and blue ; it ultimately becomes acid. 

Acidity. — This is due to the fermentation of milk sugar and the 
production of lactic acid. The degree of acidity is determined by the 
titration of 5 cc. of milk (previously diluted with 50 cc. of water) by a 
solution of tenth normal sodium hydrate, using phenol-phthalein as an 
indicator. The acidity may be expressed in cubic centimeters of sodium 
hydrate, or each tenth of a cubic centimeter may be considered as a 
degree of acidity. For example, six hours after milking the acidity may 



be fourteen to twenty-five degrees ; forty-eight hours after milking it 
may reach one hundred degrees. When the acidity reaches twenty-three 
degrees milk coagulates on boiling. {^Analyst, vol. xvi, p. 200.) An 
example of the rate of change is given in the following table : 



Day. 


Acidity. 


Sugar. 


cc. 


Degrees of rotation. 


I 


2.2 


25.2 


2 


5-5 


23.1 


3 


II. 


21.6 


6 


13.2 


14.2 


7 


15.0 


9.4 


8 


16.3 


7.8 


9 


17.2 


1.2 



" Thesis;' Ethel B. Blackwell, M. I. T., i8gi. 

Alkalinity or Ammonia. — The nitrogenous constituents of milk are 
also subject to fermentation or decomposition by means of the growth 
of bacteria. Ammonia (or a substance which yields ammonia on distil- 
lation) is formed, and tends to neutralize the lactic acid. On the other 
hand, abundant acid tends to check the growth of the alkaline ferments. 
It depends upon certain conditions of seeding and of temperature which 
gets the best start in the race. It is to the alkaline fermentation that 
most of the danger in using unsterilized milk is due. 

DETERMINATION OF ALKALINITY OR AMMONIA. 
APPARATUS REQUIRED. 

25 CC. pipette; Kjeldahl distilling flask ; 250 cc. receiving flask ; 2 burettes. 

CHEMICALS REQUIRED. 

Sodium carbonate ; sulphuric acid i : 40 ; ^j^ hydrochloric acid ; j'J, sodium hydrate ; 
phenolphthalein 1:500 in 90 per cent, alcohol. 

25 CC. of the milk to be tested are delivered from a pipette into 
a Kjeldahl distilling flask. 350 cc. ammonia free water and .5 gram 
sodium carbonate are added. About 200 cc. are then distilled into a 
250 cc. receiving flask containing about 20 cc. sulphuric acid i : 40. 
This distillate is redistilled, with the addition of .5 gram sodium car- 
bonate, or enough to neutralize the acid present, in order to convert into 
ammonia any amines formed during the first distillation ; or enough 
alkaline permanganate to give a decided pink color may be used in- 
stead of the sodium carbonate. The distillate is received into 15 cc. 
of T^ hydrochloric acid and titrated with /^ sodium hydrate. Phenol- 
phthalein is used as an indicator. 



TOTAL SOLIDS. 

Wanklyn's Method. 

APPARATUS REQUIRED. 

Shallow platinum dishes of about five square inches bottom area (blacking box 
covers answer very well) ; 5 cc. burette pipette ; beakers. 

The shallow platinum dish is weighed and left on the balance pan ; 
5 grams are added to the weights upon the other pan, and 5 cc. of the 
well-mixed milk, measured from the burette pipette, are delivered into 
the dish, and the whole weighed as rapidly as possible, the movement 
of the rider probably sufificing. The milk is evaporated to dryness upon 
a water bath, and dried at 100° to a constant weight. Dr. Davenport 
dries at 105°; Wanklyn recommends drying three hours each time, and 
not weighing a second time ; and Gerber advises coagulation by abso- 
lute alcohol before evaporation, 

REFERENCES. 

Wanklyn, Milk Analysis. 
Gerber, Milch Analyse. 

FAT. 

/. Wanklyn's Method. 

APPARATUS REQUIRED. 

As in total solids, pincers ; gasolene wash bottle ; glas> rods. 

CHEMICALS REQUIRED. 

Gasolene, sp. gr. 86° B., which leaves no residue. 

The dried and weighed residue from the determination of total 
solids is treated in a warm place with gasolene. After about fifteen 
minutes the gasolene is decanted off and the residue treated with a 
fresh portion. Six portions will suffice. Finally the dish is held with 
the pincers and the outside and rim carefully washed off by a stream 
of gasolene from the wash bottle, to insure the removal of all the fat. 
The residue is dried and weighed, and the difference between this weight 
and the original is the weight of the fat. The results are about 0.2 per 
cent, lower than those obtained by other methods, as the fat is not in 
a condition to be readily extracted. 

REFERENCE. 

Davenport, Alass. Stiite Bd. of Health Ref^l, xviii, 1886, p. 139. 



7 

2. Adams' Method. 

APPARATUS REQUIRED. 

Return flow condenser; Soxhlet's extractor ; wide-mouthed lOO cc. flasks ; large 
beaker for a water bath (if a special bath is not at hand) ; 5 cc. pipette ; extracted filter 
paper in strips 22 inches long by if inches wide. 

CHEMICALS REQUIRED. 

Gasolene, sp. gr. 86° B., which leaves no residue. 

Absorbent paper exercises a selective action on the constituents 
of mills, so that the fat is left on the surface of the paper mixed with 
only about one third of the non-fatty solids, and hence it is more easily 
extracted. The strip of paper may be pinned by one corner, so as 
to hang free ; 5 cc. of the milk to be tested are run on to the upper 
end from a pipette. When dry the paper is carefully rolled into a coil, 
placed in the extractor, and treated with gasolene for about two hours ; 
or the coil may be made first, and the milk run on to it. The flask, 
previously tared, is weighed after the evaporation of the gasolene, and 
the increase in weight is the fat. 

3. The Babcock Method. 

The fat is freed from the other constituents and collected in the 
graduated neck of the bottle for measurement. 

APPARATUS REQUIRED. 

Centrifugal machine; whirling bottles ; 17.6 cc. pipette ; 17.5 cc. graduate ; wash 
bottle containing boiling water. 

CHEMICALS REQUIRED. 

Sulphuric acid, 1.835 ^P- S''- 

17.6 cc. of the milk to be tested are delivered from a pipette 
into a long-necked graduated whirling bottle. 17.5 cc. sulphuric acid, 
1.835 ^P- &•"•' ^'"^ gradually added, with vigorous shaking after each ad- 
dition of acid. The sulphuric acid should blacken the milk and cause 
a considerable amount of heat. After the acid is added and before the 
bottles are allowed to cool they should be whirled. They are to be 
placed in opposite pockets, in even numbers, and whirled for six to 
seven minutes, the large wheel making eighty to ninety revolutions per 
minute. The bottles are then removed, and the hot water, which should 
be ready by this time, is added to each bottle until the surface of the 



8 

mixture rises nearly to the top of tlie graduations on the neck. The 
bottles are again placed in the whirler, and turned at about the same 
rate for one minute. At the end of this time the bottles can be taken 
out and the length of the column of fat measured by dividers, one 
point of which is placed at the bottom and the other at the upper limit 
of the fat. If one point of the dividers is then placed at the zero mark 
of the scale on the bottle used, the other will be at the per cent, of fat in 
the milk examined. 

RELATION BETWEEN SPECIFIC GRAVITY, FAT, AND SOLIDS IN MILK. 

The specific gravity of milk is, in the main, a function of two fac- 
tors, namely, the percentage of solids not fat and that of the fat. The 
former raises it ; the latter lowers it. Taken by itself it afTords very 
little indication of the composition, but if any other item be known 
it should be possible to find, by calculation, the other quantities, pro- 
vided the assumption is true. The solids not fat are made up of sev- 
eral fluctuating constituents, but "normal milk " seems to contain them 
in such a constant ratio that a calculation serves at least to detect 
an abnormal sample. 



Specific gravity 



Of fat. 



•93 



Of casein and albumen Of sugar. 



1-34 



1.65 



Of ash. 



3-0 





Ash. 


Proteid. 


Sugar. 


Ratio in normal milif 


2 


9 


13 



EXAMPLE. 

Given the specific gravity and solids, to calculate the fat: 
Specific gravity = Gr. The amount which each per cent, of solids 
not fat raises the specific gravity = ^. The amount which each per cent, 
of fat lowers the specific gravity = f. Total solids = T. Solids not 
fat = 6". Fat = 7^ Gr =z Ss — Ff; or, substituting for 6' its value 
T — F, Gr ^:^ {T — F)s — Ff. The uncertainty of the calulation lies 
in the values of s and y^ which have not been quite satisfactorily deter- 
mined. 



6 G 

The simple formula /^ = T — — answers within the limits of 

5 4 

experimental error for normal milk, but not for skimmed or watered milk. 

Data: Gr = 1.0323. G = Gr — i X 1000 = 32.3. T= 12.90. 

g 22 1 Calcul.ited. Found. 

~jF = 12.90 — ~ = 4.02 3.99. 

A similar relation has been worked out for the proteids and sugar, 
so that from three determinations the whole composition may be cal- 
culated. Example as above : 

G 

Ash = .70 = A. Formula/^ = 2.8 T + 2.5.^ — 3.33/^" — .68 .. ^. ' 

or, F --= 36.12 + 1.75 — 13.32 — 21.28 = 3.27. 

Sugar = r — {A -\- P i- F). 

Sugar = 12.90 — (.70 + 3.27 + 4.02) = 4.91. 

CHIEF REFERENCES. 

Analyst, vol. vii, p. 129. 
Analyst, vol. xiii, pp. 26 and 49. 

With Chart. 
Analyst, vol. xv, p. 170. 
Analyst, vol. xvii, p. 169. 
Analyst, vol. x.x, pp. 7 and 57. 

SUGAR. 

/. By Titration with Fehlin^s Solution. 

APPARATUS REQUIRED. 

Pipettes 25 cc. and 5 cc, also i cc. divided into hundredths; 50 cc. graduate; 
250 CO. bottle ; 500 cc. graduated flask ; burettes; thermometers; water bath ; beakers; 
4-inch casserole or a 6- inch porcelain dish ; funnels; folded filters; medicine dropper ; 
extra small filters. 

CHEMICALS REQUIRED. 

69.28 grams C. P. cojjper sulphate to i liter water; 346 grams sodium potassium 
tartrate and 80 grams sodium hydrate in i liter; acetic acid, 25 per cent, solution; 
potassium ferrocyanide, 1:50 made the day it is to be used; aluminum hydrate, as 
used for chlorine in water. See notes on Water Analysis. 

Any method of clarification may be used. The following answers very well. 

25 CC. of milk are measured into a 250 cc. bottle ; 15 cc. of aluminum 
hydrate, 75 cc. of hot water, and 0.5 cc. of acetic acid (25 per cent, solu- 
tion) are added. The bottle is tightly stoppered, shaken vigorously, and 



lO 

placed on its side to allow the precipitate to settle, after which the almost 
clear liquid is decanted into a beaker. The precipitate in the bottle is 
washed three times with hot water, by decantation, the washings being 
poured into the beaker. The contents of beaker and bottle are then 
thrown upon a 6-inch filter, and the precipitate is washed until the 
volume of the filtrate reaches 500 cc. 

Titration. — z^ cc. of the copper solution and 5 cc. of the alkaline 
tartrate are accurately measured out into the 4-inch casserole or 6-inch 
porcelain dish, diluted with 40 cc. of water, and heated to boiling. The 
whey as above prepared is added from a burette as long as a blue color 
is seen in the liquid, which must be kept constantly boiling and made up 
to ^O cc. When the end-point is nearly reached a test for copper should 
be made in the solution. To this end a few drops of the liquid are run 
from a medicine dropper through a very small filter into a test-tube, or 
on to a porcelain plate, containing a dilute solution of potassium ferro- 
cyanide strongly acidulated with acetic acid, when, if copper be present, 
the characteristic rose coloration will appear. This will give the approx- 
imate number of cubic centimeters required to decolorize the copper 
solution. 

The exact number may be most conveniently found by adding the 
quantity of whey above used to a fresh portion (10 cc.) of Fehling's 
solution and 40 cc. of water, boiling exactly two minutes, filtering the 
whole through a 4-inch filter, and testing the filtrate as above described. 

If copper be still present, the operation is repeated with 0.2 cc. more 
whey until the end-point is reached; or, if the drop of solution be color- 
less, 0.2 cc. less of the whey is used each time until copper appears. If 
10 cc. of Fehling's solution of the strength given are reduced by 0.067 

500 X .067 

gram of milk sugar, then -r; \ 3 = gram^ of milk sugar in 

° ° ' No. cc. whey used ^ ° 

25 cc. of the milk. The results are reported in per cent. From 27 to 
2)2^ cc. of whey are usually required to reduce 10 cc. of Fehling's solu- 
tion. A standardization of the reagent with pure milk sugar should be 
made. 

The cuprous oxide formed may be filtered off, washed, dissolved 
in nitric acid, and the copper determined by the battery, in which case 
larger quantities may be employed. 

REFERENCES. 

Colby, New York State Bd. of Health Reft, 1882, p. 611. 
Beckmann, Fres. Zeit., xxv, 529. 
Beckmaiin, 7 lie Analyst, xi, 235. 



II 

2. By the Saccharimeter. 

The necessary clarification is made either with basic ]ead acetate, 
acid mercuric nitrate, or mercuric iodide, and the resulting whey polar- 
ized. (See Bulletin No. 28, U. S. Department Agriculture, p. 208, 1890.) 

NITROGENOUS MATTERS CASEIN, ALBUMEN, ETC. 

5 grams of milk are used and treated as in the notes upon the 
" Determination of Nitrogen by the Kjeldahl Process," which see. 

ASH. 

The residue in the platinum dish from the extraction of fat accord- 
ing to Method i is ignited at a low red heat. 

ADULTERANTS. 

Water. — The presence of nitrates indicates that the milk has 
been watered. Uffelman {77ie Afialyst, x, 146) recommends the follow- 
ing method for their detection. Diphenylamine the size of half a pea 
is dissolved in 25 drops sulphuric acid in a 3 inch porcelain dish. A few 
drops of the suspected milk are allowed to trickle down the sides of the 
dish, when, if nitrates be present, at the point of meeting a bluish stripe 
will form and ultimately tint the whole mixture. The picric acid method 
(see notes on Water Analysis) may also be used. 

Determination of Water Added to Milk. 

For a quantitative estimation of the amount of added water Radliscu 
{Mitth. a. d. p/iartn. Inst. u. Labor, d. Univ. Eriatigen, Hi/ger, Heft, iii, 
pp. 93-112) recommends the determination of the specific gravity of the 
whey, or " serum," as he terms it. 

APPARATUS REQUIRED. 

loocc. pijjette ; 2 cc. pipette; beakers; funnels ; vvate: Isatli ; thermometer; filters; 
Westphal balance. 

CHEMICALS REQUIRED. 

Acetic acid, 25 per cent, solution. 

100 CC. of the milk are thoroughly mixed in a beaker with 2 cc. of 
the acetic acid, and heated in a water bath at 85° C. for five to ten 
minutes. The casein is by this treatment precipitated as a compact 
cake, and is easily filtered off. The contents of the beaker are now 
filtered, care being taken to bring as little of the precipitate upon the 



12 

filter as possible ; the filtrate, carefully mixed, is cooled to 15° C, and its 
specific gravity taken by the Westphal balance. Radliscu finds that the 
specific gravity of the whey or serum in a normal milk is never below 
1.027, that it contains 6.3 to 7.5 per cent, total solids, of which .22 to 
.28 per cent, are fat. The addition of each 10 per cent, of water lowers 
the spe'cific gravity by .0005 to .0010, and the percentage of total solids 
from 0.3 to 0.5 per cent. 

OTHER SUBSTANCES. 

Salt. — Detected by the high percentage of ash, and determined 
volumetrically by silver nitrate after clarification with alumina. 

Caiie Sugar. — Detected by the polariscope. 

Starch. — 5 cc. of the milk warmed in a small beaker are treated 
with a few drops of iodine solution when the characteristic blue color 
indicates starch. 

Niter. — Detected in the ash. 

COLORING MATTERS. 

Annatto, caramel, and carrot extract are the substances usually 
employed to color watered milk. Thoms [Pharni. Zeit., xxxii, 59) found 
ultramarine in milk. 

A?inatto. — Dr. Davenport {Mass. State Bd. of Health Rep''t., xvi, 140) 
recommends the following method: A strip of filter paper is placed in 
the milk to be tested, previously made alkaline with carbonate of soda, 
and after being allowed to remain twelve hours is washed out. If 
annatto be present it will have acquired a salmon or light copper tint. 
This color is changed by sulphuric acid to dark blue ; by stannous 
chloride to a pink. 

Caramel. — See Fres. Zeit., xxiv, 30 ; The Analyst., x, 36. 

For other coloring matters see Leeds, '/Vie Analyst, xii, 150. 

PRESERVATIVES. 

Salicylic Acid. — A few drops of ferric chloride are added to 5 cc. 
of the milk. Should salicylic acid be present, a dirty purple to violet 
coloration is produced. 

Formalin or Fontiic Aldehyde. — This has recently come into use ; 
the odor usually betrays it. {Chem. News, vol. Ixxi, page 247.) 

Boric Acid. — Hilger {Nahr. und Genussniitteln) recommends the fol- 
lowing process: Five drops calcium hydrate are added to 10 (or 100) cc. 



13 

of the milk and evaporated to dryness on a water bath. The residue is 
charred, a few drops of water are added, the liquid is made slightly acid 
with hydrochloric acid, and filtered into a porcelain dish. The usual 
qualitative test with alcohol or turmeric paper is applied. (See also 
Kretschmar, The Analyst, xii, 159.) 

Benzoic Acid. — Fres. Zeit., xxi, 531 ; Jour. Anal. Chem., ii, 446. 

Carbonate of Soda. — Detected in the ash. 

Hydrogen Peroxide. — See Hilger, loc. cit., p. 58. See also Stokes, 
The Analyst, xvi, 123. 

BUTTER ANALYSIS. 

General Statements. — Butter consists of the fat of milk, together 
with a small percentage of water, salt, and curd; these exist in about 
the following proportions: 

Fat, 7S. 00-90.0 per cent.; average, 82 percent. 

Water, 5.00-20.0 " " " 12 " " 

Salt, 0.4 -15.0 " " " 5 " " 

Curd, 0.1 1- 5.3 " " " I " " 

The fat consists of a mixture of the glycerides of '' the fatty acids," 
which, when saponified, yield an increased weight of product, owing to 
the combination of water in the process. One sample gave 106.32 parts 
from one hundred parts of fat containing 12.5 per cent, of glycerine. 
(For further discussion see Analysis and Adulteration of Food, James Bell. 
On the constitution of butter fat see Analyst, vol. xvi, p. 161.) 

The fatty acids have a very complex composition, not yet perfectly 
understood. The Danish chemist Koefoed gives the following as the 
proportion of the acids thus far isolated : 

Oleic acid, C17H33COOH ) Per cent. 

Acid of the formula, C1SH28O4 f 34.0 
Acid of the formula, C29H54O5 ) 
(The latter is probably a mixture.) 

Stearic acid, C17H35COOH 2.0 

Palmitic acid, CisHsiCOOEi 2S.0 

Myristic acid, C13H07COOH 22.0 

Laurie acid, C11H23COOH 8.0 

Capric acid, Cg H19COOH 2.0 

Capryjic acid, C7 H15COOH 0.5 

Caproic acid, C5 HuCOOH 2.0 

Butyric acid, C3 H7 COOH 1.5 

Analyst, vol. xvii, p. 130. 



The examination, from a sanitary standpoint, consists in the deter- 
mination of the quantity and condition of the curd and in the test for 
gelatin, since it is probably only in the possible decomposition of the 
nitrogenous portion that danger to health lies. It is now well recog- 
nized that the addition of oleomargarine is not injurious to health. It 
hns become, however, a not infrequent practice to secure an admixture 
of a large per cent, (as high as ;^^ per cent.) of curd or other nitrogenous 
material in certain fresh butters. If this mixture is eaten at once there 
is no danger; but on keeping, a decomposition occurs which is liable 
to produce serious effects. The percentage composition of the butter 
has, therefore, a sanitary as well as an economic aspect. 

The "aroma" of butter seems to be connected with the decomposi- 
tions caused by the growth of bacteria on the sugar and casein, and not 
by a change in the fats ; but there is no evidence that any unwholesome 
effect is produced. 

The usual examination consists in the determination of fat, water, 
salt, and curd. 

EXAMINATION OF THE FAT. 

The butter fat is isolated, saponified, and the volatile fatty acids 
are determined by distillation and titration, as in the Reichert method ; 
or they are washed out and the fixed fatty acids weighed, as in the 
Hehner method; or the weight of iodine required to saturate the acids 
is found by the Hiibl method. 

APPARATUS REQUIRED. 

Tall 30 cc. l)eakers; pipette with bulb, graduated to deliver 5.75 cc. water; 250 
cc. round-bottomed flasks; no cc. graduated flasks; 100 cc. graduated flasks; 100 cc. 
graduated cylinder ; beakers ; funnels and filters. 

CHEMICALS REQUIRED. 

Absorbent cotton; sulphuric acid i : 40 ; potassium or sodium hydrate r : i; 
95 per cent, alcohol redistilled from potassium hydrate; IJ, sodium hydrate; ^^ barium 
hydrate; phenolphthalein 1:500 in 90 per cent, alcohol; bits of ignited pumice 
dropped while hot into water and bottled for use. 

Procedure. — A piece of butter — about a cubic inch — is melted in 
a small narrow beaker placed in the water bath. After about fifteen 
minutes, during which time the temperature should have risen not above 
60° to 70°, the water, salt, and curd will have settled to the bottom, and 
the clear fat may be decanted into a similar beaker through absorbent 
cotton or asbestos, care being taken that none of the water or curd is 



15 

brought upon the filter. When the filtered fat has cooled to about 40° 
the pipette is placed in the beaker and the whole weighed. 

By means of the pipette about 5 grams of fat are transferred to 
a dry 250 cc. round-bottomed flask, the pipette replaced in the beaker, 
and the whole again weighed. The difference in weight gives the exact 
quantity of fat taken. It is a saving of time, if several portions are to 
be weighed out, to make the weights one after the other, so that one 
weight will sufifice for a determination. Weigh off thus : Two portions 
of 5 grams each into the round-bottomed flasks for Reichert's method, 
a portion of 2.5 to 3 grams into a 500 cc. beaker for Hehner's process, 
two portions of about a gram each into 300 cc. bottles for Hiibl's process. 

/. Reichert-Meissl Number for Volatile Fatty Acids. 

To the fat in the 250 cc. round-bottomed flnsks are added 2 cc. of 
the caustic potash and 10 cc. of 95 per cent, alcohol. (The addition 
of 3 cc. ether, and then a vigorous boiling, reduce the time of saponifi- 
cation to a few minutes, or even seconds.) The flasks are then con- 
nected with long, straight glass tubes, serving as return flow condensers, 
and placed upon the water bath until saponification is complete ; fre- 
quent shaking hastens the process. When this has taken place the 
flasks are disconnected and the alcohol evaporated. After the complete 
removal of the alcohol, 100 cc. of boiled distilled water, at a temperature 
of about 50^^, are slowly added from a graduate, and the soap dissolved 
by gently warming on the water bath. Rapid addition of water may de- 
compose the soap, setting free the fatty acids : 

C17H35COOK + HoO = C17H35COOH ^ KOH. 

When the solution of soap has cooled to 60° or 70°, it being per- 
fectly clear, 50 cc. of the dilute sulphuric acid are added to set free the 
fatty acids. Two bits of pumice are dropped into the flask, which is 
then closed by a cork lied in with twine and immersed in boiling water 
until the fatty acids have melted to an oily layer floating on the top 
of the liquid. It is then cooled to 60°, the cork removed, and the flask 
attached to the condenser. 

The distillation should be so conducted that 110 cc. come over 
in thirty minutes. 

The distillate, after being thoroughly mixed, is poured through 
a dry filter, and 100 cc. are titrated with y^ barium or sodium hydrate, 
using phenolphthalein as an indicator. The number of cubic centime- 



i6 



ters of alkali used is increased one tenth, and the weight of fat cor- 
rected for any number greater or less than 5 grams. 

For example, if 5.3 grams butter fat are used, and 100 cc. of the 
distillate require 27.4 cc. Ba(0H)2, iiocc. would require 27.4 -|- 2.74 
= 30.14 cc. Then 5.3 : 30.14 :: 5 : a\ x ^= 28.4. 

X is the Reichert-Meissl number. Butters which give a number 
over 27 and under 30 may be considered genuine. Those which give 
a number between 25 and 27 are somewhat doubtful, and those which 
give less than 25 should be looked upon with suspicion. 





French Buttek. 


English Buttek. 




Fresh. 


Salt. 


Salt, 


Fat 

Water 

Solids not fat 

Salt : 

Reicliert luimber 


84-39 

13.98 

1. 51 

.12 

29.1 


83-44 

12.86 

..63 

2.07 

29.1 


82.9S 

13-99 
0.89 
2.14 

28.1 



REFERENCES. 

Meissl, Dingier folyt. Jojtr., ccx.x.\i, 47S. 

" Zeit. Anal. C/iem., xviii. 63. 
Sendtner, Archiv. fiir Hygiene, i, 137 ; viii, 424. 
WoUney, Analyst, xii, 203; xiii, 8. 

2. He/iner's Method for Direct Deter tnination of the Fixed Fatty Adds. 



APP,4RATUS REQUIRED. 

500 CC. beakers ; funnels ; " weighing beakers; " filters dried over sulphuric acid. 

CHEMICALS REQUIRED. 

Potassium hydrate as in t ; hydrochloric acid, 1.12 sp. gr. ; 95 percent, alcohol. 

The portion of 2,5 grams weighed out into the 500 cc. beaker is 
saponified by using i cc. potassium hydrate diluted with 20 cc. 95 per 
cent, alcohol. As it is not essential to prevent the escape of the volatile 
acids, the precautions in Method i are unnecessary, but loss by spurting 
must be avoided. 

The aqueous solution of the soap, which should be 300 to 400 cc, 
is decomposed by 10 cc. hydrochloric acid and heated in a water bath 
almost to boiling until the clear oil floats. The beaker and contents are 
allowed to become quite cold ; the clear liquid, and finally the solid fats, 
are brought upon the thick weighed filter. When the beaker and fat are 



17 

well washed with cold water, the adhering fat is washed out with boiling 
water, which is poured through the filter, taking care that the filter is 
never more than two thirds full. The funnel is cooled by plunging it 
into cold water, the filter removed, placed in a weighing beaker dried 
at ioo° and weighed as soon as practicable, since long heating causes 
oxidation. A weight constant within 2 mgs. is sufficiently accurate. 

Eighty-seven and one half per cent, is usually taken as the propor- 
tion of fixed fatty acids in butter; 88 and 89 per cent, have been fre- 
quently found. All other fats yield from 95 to 96 per cent, insoluble 
fatty acids. 

REFERENCES. 

Bitlter^ its Analysis and Adulteration, Hehner and Angell. 
Uietzell and Kresner, Fres. Zeit., xviii, 83. 
Heintz, Fres. Zeit., xvii, 160. 
Heliner, FVes. Zeit.f xvi, 149. 

J. Method of Baron Hubl. 

This depends upon the fact that certain of the fatty acids, notably 
the "unsaturated acids," as oleic acid, C17H33COOH, take up the halo- 
gens with the formation of addition-products. 

ATPARATUS REQUIRED. 

300 cc. glass-stopi^eied white glass bottles; glass-stoppered burettes; graduates. 

CHEMICALS REQUIREt). 

25 grams iodine in 500 cc. 95 per cent, alcohol ; 30 grams mercuric chloride in 
500 cc. 95 per cent, alcohol; the two are mixed, and after standing 24 hours are 
filtered; f;, sodium thiosulphate (24.6 grams to i liter); starch paste i '. 200; potas- 
sium iodide 150 grams to i liter; potassium bichromate C. P. 3.874 grams to i liter; 
strong hydrochloric acid; chloroform. 

The butter fat, weighed into the 300 cc. bottles, is dissolved in 
10 cc. of dry chloroform. About 30 cc. — in the case of a doubtful 
butter 50 cc. — of the iodo-mercuric solution are accurately measured 
from a glass-stoppered burette, and the bottle is allowed to stand, with 
frequent shaking, for three hours in a dark closet. About 100 cc. of 
distilled water, with 20 cc. potassium iodide, are then added — the latter 
for the purpose of keeping in solution mercuric salts — and the excess 
of iodine uncombined with fat is titrated with ^^^ thiosulphate. When 
the solution has become faintly yellow, a few drops of freshly prepared 
starch solution are added and the titration continued to disappearance 
of the blue color. 



i8 

The results are calculated in grams of iodine absorbed by loo 
grams of fat. This is frequently called the Hiibl or Iodine absorbtion 
number. 

Standardization of the lodo-Merairic Solution. — Since the strength 
of this solution is liable to change, the relation between it and the 
thiosulphate should be determined by carrying through a blank in the 
same manner and with the same quantities of reagents as in the case 
of the fat. 

Stafidardization of the Thiosulphate Solution. — As this is not per- 
n)anent, its strength should be determined by means of the standard 
solution of potassium bichromate, i cc. of which liberates o.oi gram 
of iodine. 

About 20 cc. of potassium bichromate are accurately measured 
from a burette into a 300 cc. glass-stoppered bottle, 10 cc. of potassium 
iodide and 5 cc. strong hydrochloric acid added, and the iodine which 
is set free is titrated with thiosulphate as above directed: 

KoCrsO; + HHCi + 6KI = 8KC1 + Cr-jCls + 7H..O + 61. 

CALCULATION OF RESULTS EXAMPLE. 

STANDARDIZATION OF THIOSULPHATE SOLUTION. 

17.2 CC. thiosulphate = 21.5 cc. bichroniaie = 0.215 gram iodine. 
I cc. thiosulphate = 0.0125 gram iodine. 

STANDARDIZATION OF IODINE SOLUTION. 

31 cc. ioditie solution = 46 5 cc. thiosulphate. 
I cc. iodnie solution = 1.5 cc. thiosulphate. 

If 31 cc. iodine solution have been added to 1.049 g'ams of fat, then 31.0 X 1.5 
= 46.5 cc. is the equivalent amount of thiosulphate solution; and if 19.4 cc. tliio- 
sulphate were used to titrate excess of free iodine, 46.5 — 19.4 = 27.1 cc. is the 
amount of thiosulphate equivalent to iodine combined with the fat. Then since i cc. 

thiosulphate is equivalent to 0.0125 free iodine, ~-Ll '. — :iJ X 100 = 32.29 grams 

I 049 
of iodine combined witii 100 grams fat. 

It is assumed that 100 grams pure butter absorb 30 to 40 grams 
iodine; artificial butter, 55 grams; oleomargarine, 63 to 75 grams; olive 
oil, 83 grams ; and cottonseed oil, 106 grams. 

REFERENCES. 

Hiibl, Dinnler polyt. Jour., ccliii, 281. 
Join-. Soc. Chem. Ind., iii, 641. 
Pattinson, y<?«r. Soc. Chem. Iitd., viii, 30. 
Williams, T/ie Analyst, xiv, 103. 
Hehner, T/te Analyst, xx, 49, 176, 280. 



19 

PHYSICAL METHODS. 

Microscopic Examination. — The student is referred to Bulletin No. 
13, U. S. Dept. of Agriculture, Part I, pp. 29-40; Part IV, pp. 449-455. 

Specific Gravity. — This is most conveniently determined at 100° C. 
by means of the VVestphal balance (see Allen, The Analyst., xi, 223 ; 
also the Bulletin, Part IV, pp. 430-431.) The pyknometer method is, 
however, the one adopted by the Association of Official Agricultural 
Chemists, to w^hose report (Bulletin No. 28, 1890, p. 196) reference is 
made. 

Melting Point. — This is best determined according to the direc- 
tions given in the Bulletin just mentioned, p. 198. 

Refractive Index. — See Bulletin No. 28, p. 207. 

DETERMINATION OF WATER. 

About 2 grams of butter are weighed in a shallow dish having a 
flat bottom two inches in diameter and containing a slender stirring- 
rod two and a half inches long. The butter is heated in the oven at 
100° C. for thirty minutes, cooled in a desiccator, and weighed. It is 
then heated again for periods of fifteen minutes, and weighed until the 
weight remains constant. During the process of heating the butter 
should be frequently stirred, to hasten evaporation of the water. The 
loss in weight is calculated as water, although a portion of the volatile 
acids is also lost, the amount depending upon the time of heating. 

DETERMINATION OF SALT. 

10 grams of the butter are weighed in a small beaker, 30 cc. of 
hot water added, and, when the fat has completely melted, the whole 
transferred to a separatory funnel. The contents are thoroughly shaken, 
the fat allowed to rise to the top, and the water drawn off. 30 cc. of 
water are again added, and the operation repeated until washings are 
obtained which give but a faint turbidity when tested with silver nitrate. 
The washings are thoroughly mixed, made up to 250 cc, and 25 cc. 
titrated for chlorine in a six-inch porcelain dish, using ^^ silver nitrate 
with potassium chromate as an indicator. 

DETERMINATION OF CASEIN. 

Estimated by Kjeldahl's process for the determination of nitrogen. 

DETECTION OF COLORING MATTERS. 

5 grams of the filtered butter fat are dissolved in a separatory fun- 
nel in 25 cc. of ether ; 25 cc. of water, rendered faintly alkaline with 



20 

sodium hydrate, are now added, and the mixture thoroughly shaken. 
The water dissolves the coloring matter, which may be investigated ac- 
cording to the directions for coloring matter in milk. 

REFERENCES. 

Martin, The Analyst, x, 163. 
Moore, The Analyst, xi, 163. 

APPROXIMATE DETERMINATION OF WATER, SALT, AND CURD. 

Hoorn's Method Modified. 
Place about 20 grams of butter in an open tube, and with a glass 
rod as a piston force the butter out into a test tube about 12 inches in 
leno-th and i inch in diameter. Add 40 cc. gasolene, cork the tube 
securely, and shake vigorously; allow to settle, and siphon off the clear 
upper layer ; add 40 cc. more gasolene, and repeat. Wash into the grad- 
uated Hoorn tube, allow the contents to settle, read off the amount of 
water and matters not fat. 

REFERENCE. 

Hoorn, Fies. Zeit., xi, 334. 

FLOUR, PREPARED CEREALS, ETC. 
This class of food stuffs is usually in a dry form and not liable to 
rapid change by micro-organisms, and the examination consists in the 
determination of their "food value." This may require a simple analyt- 
ical process, as in the case of the quantity of nitrogen in a sample of 
"o-luten " sold for diabetic patients, or in case of a brand of flour used 
in a hospital, or State institution. It may also require an estimation 
of the available food material, as in the case of two kinds of beans 
or corn. The actual determination of digestibility belongs rather to 
physiological than to sanitary chemistry. 

TOTAL NITROGEN IN CEREALS AND OTHER ORGANIC SUBSTANCES 
CONTAINING COMBINED NITROGEN. 

By KjeldahVs Process. 

APPARATUS REQUIRED. 

Block tin condensers; 750 cc. round- 1:)ottomed flasks; 250 cc. flat-bottomed 
flasks; digestion flaslis; graduates. 

CHEMICALS REQUIRED. 

Sodium hydrate (sp. gr. 1.31); /o hydrochloric acid; i^g sodium hydrate; mer- 
cury; potassium sulphide, 40 grams to liter; methyl orange No. Ill, rosolic acid or 
cochineal ; sulphuric acid, free from nitrogen. 



21 

Prhidph. — Oxidation of carbon and hydrogen, and conversion of 
organic nitrogen to ammonium sulphate by means of boiling sulphuric 
acid in presence of mercury, the latter acting as a carrier of oxygen, 
and being converted to mercuric sulphate. Precipitation of mercury by 
potassium sulphide to prevent the formation of mercur-ammonium com- 
pounds when the solution is made alkaline. Setting free of ammonia 
by neutralization of acid with sodium hydrate. Distillation of ammonia 
into a measured quantity of y^ hydrochloric acid. Titration of excess 
of acid. 

About 0.5 gram of the finely divided substance are transferred 
from a weighing tube to a digestion flask, 10 cc. strong sulphuric 
acid, free from nitrogen, and 0.2 gram metallic mercury added, and 
the flask is placed on a wire gauze under the hood. Gentle heat is 
applied until frothing has ceased and the liquid boils quietly. The 
flame is then increased and boiling continued until the solution becomes 
colorless. The flask is now allowed to cool for a minute, and a few 
crystals of potassium permanganate cautiously added, until the liquid 
has acquired a slight green or purple color. The condenser should at 
the same time be freed from ammonia by distillation with pure water, 
until a slight color only is given to 50 cc. of the distillate by Nessler's 
solution. About 25 cc. j^i hydrochloric acid are carefully measured 
from a burette into a 250 cc. flask, and the condenser-tip placed beneath 
the surface of the liquid, a little water being added, if necessary, to seal 
it. About 100 cc. distilled water are now cautiously added to the liquid 
in the digestion flask, the whole transferred to a 750 cc. round-bottomed 
flask, and the former rinsed out with 100 cc. more water. Mercury is 
precipitated by the addition of about 20 cc. potassium sulphide, and 
finally 65 to 70 cc. sodium hydrate (sp. gr. 1.3 1) are carefully run 
down the side of the flask, in order, so far as possible, to avoid mix- 
ing with the acid liquid. If this precaution is neglected, ammonia 
may be lost. The flask is now connected with the condenser, and the 
contents thoroughly mixed by a gentle rotary motion. A low flame 
siiould be applied until the contents of the flask are thoroughly warmed, 
then increased until the liquid boils briskly, care being taken that none 
comes in contact with the cork. When 200 cc. have di-^tilled over, the 
collecting flask is removed, after rinsing off the condenser-tip with dis- 
tilled water, and the excess of acid titrated with /^ sodium hydrate, 
using methyl orange or cochineal as indicator. Blanks should be car- 
ried through in the same way. 



22 



CALCULATION OF RESULTS. 



If rt! = no. cc. ^ acid run into the small flask, a' ^= no. cc. excess acid titrated, 
and n = weight of nitrogen in sample, then n = {a — a') X .0014. 

To prevent bumping during distillation, a current of air, purified 
by passing through sulphuric acid, may be conducted into the liquid. 
If nitrates are present, see Dept. Agric. Bull. 43, p. 347. 

DETERMINATION OF STARCH. 

In the absence of a satisfactory method for the determination of 
starch applicable in all cases, the student is referred to the standard 
works. 

REFERENCES. 

Maercker, Handb. der Spiritusfabrikation, p. 77 seq. 
U. S. Dept. Agric. Bull. 43, p. 162. 
Sadtler, Indust. Org. Clievi. 

The following method (Hibbard, Jour. Am. Chem. Soc, xvii, 64) 
promises to be of use : 

Principle. — Conversion of starch to dextrin and maltose by dia- 
stase in malt extract. Conversion of dextrin and maltose to dextrose 
by acid (hydrolysis). 

The finely divided sample, which must contain 0.5 to i.o gram 
of starch, is placed in a flask with 50 cc. water, 3 cc. malt extract 
added, and boiled for one minute, with frequent shaking. The solution 
is then cooled to 60° C, 3 cc. malt extract added, and again heated 
slowly, so that fifteen minutes are required to reach the boiling point. 
It is then tested for starch by placing a drop upon a porcelain tile and 
adding a drop of solution of iodine in potassium iodide. Should a blue 
color appear, more malt extract must be added, and the boiling be re- 
peated until all starch has been converted. The solution is then cooled, 
made up to 100 cc, and filtered through fine linen or cotton cloth. An 
aliquot part of the filtrate, 25 or 50 cc, is placed in a flask with 5 cc. 
hydrochloric acid (1.15 sp. gr.), and water added to make the volume 
60 cc. A small funnel is placed in the neck of the flask to retard 
evaporation, and the solution boiled quietly for exactly half an hour. It 
is then cooled, nearly neutralized with sodium hydrate, and the dextrose 
determined by Fehling's solution. The method is simple and fairly 
accurate. A correction should be made for sugar in the malt extract. 
The malt extract is prepared by treating coarsely pulverized dry malt 
for several hours with sufficient 20 per cent, alcohol to cover it. The 
solution is then filtered, and may be kept for two weeks without losing 
its diastatic power. 



23 
EXAMINATION OF FERMENTED LIQUORS. 

WINE. 

Effervescing wines should, before analysis, be vigorously shaken in 
a large flask, to remove carbon dioxide. 

Specific Gravity. — Specific gravity is taken by means of the pyk- 
nometer or Sprengel tube at 15.5° C. 

Alcohol by Weight. — About 50 cc. of wine are weighed in a 150 cc. 
wide-mouth stoppered bottle, and transferred with 100 cc. water to a 
500 cc. round bottom distilling flask. Free acid is neutralized with 
sodium hydrate, and 0.5 gram tannin added to prevent frothing. About 
100 cc. of liquid are distilled over into the 150 cc. flask, which should 
be provided with a cork, perforated to receive the condenser-tip, and 
carrying a mercury valve to prevent loss of alcohol. The distillate, 
after being thoroughly mixed, is weighed, the specific gravity taken, 
and the percentage of absolute alcohol by weight corresponding to it 
found in the tables. 

Calculation of Results. — Calling A the percentage of absolute alco- 
hol in the sample, a that in the distillate, W and w their respective 

weights, then A = ^^. If the specific gravity of the wine is known, 

weighing may be avoided by carefully measuring both sample and dis- 
tillate at 15.5° C. The corresponding percentage of alcohol by volume 
may be found in the tables. 

Extract — Dry Wines. — About 50 cc. are weighed in a small flask, 
transferred to a platinum dish having a flat bottom, and evaporated on 
the water bath to the consistency of sirup. The residue is then heated 
in the oven at 100° C. for two hours and a half, cooled in a desiccator, 
and weighed. 

Sweet Wines. — Of these only 10 cc. are weighed, diluted to 100 
cc, and 50 cc. evaporated as above described. 

Ash. — Ash maybe determined by igniting the extract at a very 
low red heat and weighing. 

Free Acids — Total Acidity Calculated as Tartaric Acid. — 10 cc. of 
wine are titrated with ^\ sodium hydrate. The end-point is reached 
when a drop of the liquid placed upon faintly red litmus paper pro- 
duces a blue spot in the middle of the portion moistened. Number 
of cc. y'ij sodium hydrate used X -0075 = weight in grams of all acids 
reckoned as tartaric acid. 



24 

Volatile Acids Calculated as Acetic Acid. — 50 cc. of wine are accu- 
rately measured into a 300 cc. flask provided with a cork having two 
perforations. One is fitted with a tube 6 mm, in diameter and blown 
out to a bulb 40 mm. in diameter a short distance above the cork ; this 
tube is connected with a condenser. The other perforation carries a 
tube reaching nearly to the bottom of the flask and drawn out to a small 
aperture at its lower end ; this is connected with a 500 cc. flask con- 
taining water. Both flasks are heated to boiling; the flame under that 
containing the wine is then lowered and the distillation continued by 
means of steam until 200 cc. have gone over. The distillate is titrated 
with Y^ sodium hydrate, using phenolphthalein as an indicator. Num- 
ber of cc. xs^ sodium hydrate used X .0060 = weight in grams of 
volatile acids reckoned as acetic acid. 

Fixed Acids Calculated as Tartaric Acid. — These maybe found by 
calculating the volatile acids as tartaric and subtracting the result 
from the total tartaric acid found by direct titration. 

EXAMPLE. ' 

If 10 CC. wine by direct titration require 9.5 cc. ^ alliali, 50 cc. require 
47.5, therefore 47.5 X .0075 :=^ .356 grams total acid reckoned as tartaric in 50 cc. 
If the distillate from 50 cc. wine requires 4.5 cc. j^j alkali, then 4.5 X .0060 = .027 
grams volatile acid reckoned as acetic. Now 4.5 X .0075 == .034 grams tartaric acid 
and .356 — .034 =i .322 grams fixed acids reckoned as tartaric in the wine. 

Results may be calculated in percentages or as grams in 100 cc. 
wine. 

BEER AND OTHER MALT LIQUORS. 

Before analysis the sample must be thoroughly shaken in a large 
flask, in order to remove carbon dioxide. 

Specific Gravity. — Taken with the pyknometer or Sprengel tube at 

15-5° C. 

Alcohol by Weight. — Determined as in the analysis of wine, using 
100 cc. of the sample. 

Extract and Ash. — Determined as in the analysis of ^rj' wines. 

Free Acids. — Titrated as in the analysis of wine. Fixed acids, 
consisting principally of lactic and succinic, are calculated as lactic 
acid, using as a factor .0090. Volatile acids are calculated as acetic 
acid. 



25 

Nitrogen. — About 20 cc. of the sample are weighed, transferred to 
a digestion flask, and evaporated almost to dryness on the water bath. 
The nitrogen is then determined by Kjeldahl's method. 

For the determination of other constituents of fermented liquors 
see authorities referred to below : 

REFERENCES. 

U. S. Dept. Agric. Bull. 43. 
Allen, Commercial 07-ganic Anal. I. 
Sadtler, Handb. Industrial Org. Chem. 
E. Borgman, Anal, des Weines. 
Maercker, Handh. der Spiritusfabrikation. 
Moritz and Morris, Scietice of Brewing, 



26 



THE DETERMINATION OF CARBON DIOXIDE IN THE AIR 
OF BUILDINGS FOR THE PURPOSE OF ESTIMATING 
THE EFFICIENCY OF THE VENTILATION. 

The determination is made by bringing a known volume of air in 
contact with some agent by which carbon dioxide Is absorbed, forming 
a stable compound. The agents used are the hydrates of potassium, 
sodium, calcium, or barium. The first mentioned is used when it is pos- 
sible to bring large quantities of air in contact with small quantities of 
solution ; the potassium hydrate containing the carbonate may be kept 
for months (see "Transit of Venus Expedition," Co7nptes rendus, 1^83, 
No. 21). 

In the method as ordinarily carried out, calcium or barium hydrate 
is found the most convenient. The latter is preferred, since barium car- 
bonate is less soluble and the reaction is sharper. In any case it is 
essential for the complete absorption of the carbon dioxide that the 
reagent should be largely in excess, so that no more than one fifth its 
value should be used up. The air of an ordinary laboratory contains 
5 to 6 parts of CO2 per 10,000. The exhaled breath contains, on an 
average, 400 parts, hence the necessity of caution in collecting samples 
and in handling the apparatus is evident. 

THE DETERMINATION. 

APPARATUS REQUIRED. 

4 or 8 liter bottles graduated, with stoppers and caps; bellows and tube; 50 cc. 
bottles; pipettes; burettes; barometer and thermometer ; hygrometer. 

CHEMICALS REQUIRED. 

Barium hydrate i cc. = i milligram COo, approximately; sulphuric acid i cc. 
= I milligram COo exactl_y_i. rosolic acid or phenolphthalein. 

The bottles, previously clean and dry, are filled with the air to be 
tested by means of a bellows, a 6-foot rubber tube connecting them with 
a brass tube which reaches nearly to the bottom of the bottle ; fifteen 
to twenty strokes will be sufficient to fill a 4-liter bottle. In collecting 



27 

the sample, care must be taken to avoid draughts or the proximity of 
people. It will be possible to obtain duplicate samples only in empty, 
or nearly empty, rooms. Even two sides of the room will probably show 
differences, but two bottles filled side by side ought to agree within 0,05 
part per 10,000. The samples are brought into the laboratory, the tem- 
perature of which should be a trifle higher than that of the place where 
the samples were taken, and allowed to stand about half an hour, until 
they have attained its temperature. 50 cc. of the standard barium 
hydrate are now run in rapidly from a burette through the tube in the 
cork, the cap replaced, and the solution spread completely over the sides 
of the bottle while waiting three minutes for the draining of the burette. 
The bottle is now placed upon its side, and rolled or shaken at intervals 
for forty-five minutes ; the time and the shaking are essential elements in 
the complete absorption, care being taken that the whole surface of the 
bottle is moistened with the solution each time. At the time at which 
the barium hydrate is added, the temperature and barometric pressure 
should be noted. At the end of the time the bottle is well shaken, to 
insure homogeneity of the solution, the cap is removed from the tube, 
and the large bottle is inverted over the 50 cc. glass-stoppered bottle, 
so that the solution shall come in contact with the air as little as pos- 
sible. Under these conditions a full, well-stoppered bottle may safely 
stand for days before titration. An aliquot part, 25 cc, is taken for the 
titration, which should be made as rapidly as possible, a 100 cc. flask 
being used. The difference between the number of cubic centimeters of 
standard acid required to neutralize 50 cc. of barium hydrate before and 
after absorption gives the number of milligrams of dry carbonic acid in 
the sample tested. The amount of carbonic acid may be expressed in vol- 
umes, under standard conditions (0° and 760'"'"), saturated with moisture 
(Method i) or dry (Method 2). Tables for this purpose will be found 
in Fres. Quan. Anal., § 139; Ganof s Physics, §§ 355-360; Bunsen, 
Gasometrische Methoden, p. 277 ; or Landolt and Bornstein's Tables. 



CALCULATION OF RESULTS. 

Method I, — 8.570 liters of air contained 10.8 mgs. of dry CO2 ; i cc. 
CO2 saturated with moisture at 21° and 766'""'- weighs 1,79624 mgs. 

Q 

(Fres., § 139) .", 10.8 mgs. = '- = 6.013 cc. CO2 saturated with 

1.79624 

moisture. In 10,000 cc. ,", — — ^ = 7.02 parts CO2 per 10,000. 

8570 



28 

Method 2. 7'' ^ 7! [(i -f- .00366, /" — /)]. z'' = 8570 .'. v =: 

7958 cc. f = 2 1°. /° = 0°. z> : 7'== :: ^= : i^. 7958 : x :: 760 : 

(766 — 18.5) (18.5 = tension of aqueous vapor at 21°). z'^ = 7827 = 

capacity of bottle at 0° and 760"""-. i cc. CO., at 0° and 760"""- weighs 

^ 10.8 c.co ^ ^^^ 

1.9643 mgs. = 5.50 cc. -^-^ — = 7.02 parts COo per 10,000. 

1.9643 7827 

Note. — T7tii> samples are to be taken following the notes closely, and the results cal- 
culated by both methods before collecting more samples. Then some one room may he 
taken, and the quality of the air determined for the different hours of the day, or the 
same hour different days of the week, or a comparison of different rooms may be 
made, or a building may be tested as a whole. In making out the report of results 
they should be arranged in tabular form, attention being paid to the following points: 
Room, date, weather, barometer, time, place in room, number of people, or gas jets 
burning in room, and the condition of the doors, windows, and transoms. 

REFERENCE. 

Jour. Analyt. and Applied Chem. vol. vi., ;;63. 



29 



BIBLIOGRAPHY OF THE CHEMISTRY OF FOODS. 

A bibliography complete to 1882 may be found in the Second 
Annual Report of the New York State Board of Health. Some of 
the important works published since that time are given below: 

Allen, " Commercial Org. Analysis," 2d ed, ; Bell, "Analysis and 
Adulteration of Food ; " Church, " Food " (South Kensington Science 
Handbook); Battershall, "Food and its Adulterations;" Atwater, 
" Chem. and Economy of Food" (U. S. Dept. Agric. Bull. 21, 1895); 
Richards, " Food Materials and Their Adulteration;" Atkinson, " Sci- 
ence of Nutrition ;" Blyth, " Foods: Their Composition and Analysis;" 
Koenig, " Chemie der menschlichen Nahrungs-und Genussmittel," 3d 
auflage ; Hilger, " Vereinbarungen bet. d. Unters. u. Beurteilung v. 
Nahr. u, Genussmittel ; " " Bibliothek fiir Nahrungsmittel-Chemiker ; " 
especially, Rottger, " Kurz. Lehrb. d. Nahrungsmittel-Chemie ; " Eph- 
raim, " Originalarbeiten iiber Anal. d. Nahrungsmittel ; " Bujard and 
Baier, " Hilfsbuch fiir Nahr. Chemiker;" U. S. Dept. Agric. Bulletins 
13, 43; Boards of Health Reports; Sadtler, " Indust. Org. Chem.;" 
Wiley, "Agricultural Analyses;" Addyman, "Agricultural Analysis." 
Periodicals — "Arbeiten aus d. Kaiserl. Gesundheitsamte zu Berlin;" 
"Analyst;" "Jour. Soc. Chem. Indust.;" " Vierteljahrsschrift fiir Chem. 
d. Nahr. u. Genussmittel ;" "Milch Zeitung;" "Deutsche Viertelj. fiir 
off offentl. Gesundheitspflege ; " " Rapports du Laboratoire Municipal 
Paris." 



LABORATORY NOTES ON WATER ANALYSIS. 



(Prepared for the use of students in the Laboratory of Sanitary Chemistry of the Massachusetts 

Institute of Te'chnology. Not pubHshed.) 



CLASSIFICATION OF WATERS, 



The examination of a water in order to determine its fitness for 
domestic use (a so-called sanitary analysis) comprises the determina- 
tion of three points : first, the amount, if any, of organic matter in a 
living or dead condition suspended or dissolved in the water ; sec- 
ond, the amount and character of the products of decomposition of 
organic matter, and their relative proportions to each other ; and third, 
the amount of certain mineral substances dissolved in the water. 
From these results we draw conclusions as to the present condition 
and past history of the water. 

To facilitate this examination waters may be divided into three 
classes: first, brook, pond, and river water — so-called surface water; 
second, spring and deep well water ; third, shallow wells and sewage 
efifiuents. 

The waters of the first class found in New England are gener- 
ally more or less colored, and contain more or less suspended organic 
life and its debris, which often impart a decided odor to the water. 
These waters, draining for the most part wooded and sparsely popu- 
lated regions, are low in ammonia, nitrites, and nitrates ; low, also, in 
mineral salts, and with only a slight excess of chlorine over the 
normal. They are usually high in organic matter and albuminoid 
ammonia. 

The waters of the second class are generally odorless, colorless, 
without suspended matter or organic matter in solution, low in nitrates, 
and with nearly normal chlorine, but with higher mineral substances 
than surface waters. 



Waters of the third class present the greatest variety. They 
may be as clear and colorless and as free from organic matter as the 
second class, and they may contain more organic matter than some 
waters of the first class. As a rule, nitrates and chlorides, as well 
as mineral salts, are high ; ammonia and nitrites may or may not be 
high. 

It is always desirable to knov/ something about the origin and 
character of a water before beginning the analysis, and the foregoing 
general classification will be found helpful in planning the analysis. 
In addition to classifying a water in this way it will also be found 
useful to make three qualitative tests : first, with Nessler reagent to 
see if much free ammonia is present ; second, with silver nitrate for the 
amount of chlorine ; and third, with phenol-disulphonic acid for nitrates. 

Since the condition of the organic matter and the relation of the 
several products of decomposition to each other are constantly cfiang- 
ing, the determination of these should be begun without delay. The 
determination of the so-called " free ammonia " is first made after 
distilling the apparatus free from ammonia. Then follows the distilla- 
tion with alkaline permanganate in order to liberate the nitrogen in 
the undecomposed organic matter ; this product is called " albuminoid 
ammonia," The determination of the total combined nitrogen by the 
Kjeldahl process is to be carried on in waters of Class I at the 
same time if practicable. 

The test for the amount of nitrogen in the second product of 
decay, nitrites, is also made as soon as possible, and lastly the re- 
quired quantity of the sample is s§t aside to be evaporated for the 
determination of nitrates. 

The odor of the water is at times a valuable aid in judging the 
condition of a surface or well water. This should be determined on 
the first day and while the bottle is at least half full. It often happens 
that the color of the water gives also valuable information as to its 
condition. 

The examination for turbidity and sediment is made on the morn- 
ing of the second day after the bottle has stood over night. The color 
is estimated at any convenient time during the two days. The deter- 
mination of the carbon in the organic matter, which is in such a con- 
dition as to be oxidized to CO2 by the Kubel method by treatment 
with hot, acid, potassium permanganate solution, is next in order, and 
the results are expressed as " oxygen consumed." 

The final test for the presence of organic matter in waters of 
Class I is made by igniting the total solid residue on evaporation. 



This determination has little or no value in the case of Classes II and 
III, and is omitted as a rule. 

The residue on evaporation is often used for the determination 
of iron. 

The determination of chlorine is most essential in deciding upon 
the history of a water, since chlorine is not taken up by plant life as 
nitrogen is, and, being soluble in all combinations, it remains in the 
water when once it is there. 

Hardness is determined by means of a soap solution, and ex- 
presses approximately the amount of calcium and magnesium salts 
present. The determinations of the fixed solids, hardness, chlorine, 
nitrates, and iron, taken together, give a good idea of the character 
of the mineral matters dissolved in the water. 

Having obtained these several results, there remains the decision 
as to the present condition and past history of the water as shown by 
these tests. Briefly, the questions to be answered are these : 

I. Is the water a normal unpolluted water of its class ? that is, 
has it any more of any substance than it has a right to contain by 
virtue of its source ? A brook draining a meadow or swamp has color, 
gives high albuminoid ammonia and high oxygen consumed, but it is 
not on that account a " polluted " water. A well water may contain 
high nitrates and chlorine and yet be free from present pollution. A 
deep well water may contain high free ammonia without giving any 
evidence of pollution in historic time. To answer the question, there- 
fore, one should know the locality and surroundings of the water, its 
source, the normal chlorine, the ratio of the nitrogen compounds to 
each other, and its character as regards the permanence of the or- 
ganic matter it contains. 

II. Is the water, if normal, a good water for general domestic 
uses ? that is, is it hard or soft, has it much or little iron, has it any 
disagreeable odor? 

III. Is the water in any case safe for drinking ? To answer 
this question there is needed a knowledge wider than a chemist's of 
the relation of decaying organic matter and of the germ-carrying 
power of water to outbreaks of disease. To the chemist's knowledge 
must be added, therefore, that of the biologist, the engineer, and the 
sanitarian. 



METHODS AND REACTIONS. 



FREE AND ALBUMINOID AMMONIA. 

Since the condition of the nitrogen, as well as the relative propor- 
tion of each of the four forms in which it occurs, is one of the most 
important points to be decided, the determination of the first product 
of decay, the so-called free ammonia, is begun at once. The test 
is one of much delicacy, and requires the greatest care and cleanli- 
ness of manipulation. The top of the bottle is first rinsed under 
running water to free it from any possible dust. Under no circum- 
stances must the inside of the neck of the bottle or the stem of the 
stopper be touched by the hand or wiped with a cloth. 

After the contents of the bottle are well shaken, in order that an 
average sample may be obtained, a measured portion is distilled in the 
apparatus shown in the accompanying cut, after it has been freed 

from all traces of ammonia by dis- 
tilling in it ammonia-free water. 

Of Classes I and II 500 cc. are 
usually taken; of Class III 500 or 
less — sometimes only 10 cc. are 
used, according to the result of the 
qualitative test. To this latter class 
of waters about 0.5 gram of sodium 
carbonate is added to be sure 
that the reaction is not acid. 
Three portions of the distillate, 
of 50 cc. each, are caught in 
graduated flasks and set aside. If 
there is very much free ammonia 
present 200 cc. are distilled over. 
The time of distilling 50 cc. should 
not be more than eight or less than 
five minutes. 

After the free ammonia has 
been distilled ofiE and the contents 
of the flask have slightly cooled, 
40 cc. of alkaline permanganate are 
added through a funnel, taking care 
that no alkali touches the neck 
Scaie,ij^in.=ifoot. of thc flask, and the distillation of 




5 

the albuminoid ammonia, that is to say, the determination of the nitro- 
gen of the undecomposed organic matter, is proceeded with. For 
Class I five portions of 50 cc. each are obtained ; for Classes II 
and III only four portions are taken. This process gives about one 
half of the total combined nitrogen in the waters of Class I. 

The contents of the 50 cc. receiving flasks are transferred to 
Nessler tubes to be compared with standards which are prepared as 
follows : To the Nessler tubes nearly filled with water free from am- 
monia is added varying quantities, for instance, 0.3, 0.5, 0.7, i.o, 1.3, 
1.5, 2.0, 2.5, 4.0, 6.0 cc. of a standard solution of NH4CI containing 
.00001 gram NH3 in i cc. 

The contents of the tubes are rotated (never shaken like test tubes 
or stirred with a rod), allowed to stand two or three minutes, and 2cc. 
of the Nessler reagent added to the whole set and to the samples to be 
tested as rapidly as possible. At the end of ten minutes the colors are 
matched and the amount of ammonia recorded. As an example of a 
water of Class I may be given the following results from distilling 500 cc. : 



FREE 


AMMONIA. 


1st 50 CC. 


0.7 CC, 


2d 50 cc. 


0.3 CC. 


3d 50 cc. 


0.0 CC, 



ALBUMINOID AMMONIA. 



1st 50 CC. 


4.5 cc. 


2d 50 cc. 


2.8 cc. 


3d 50 cc. 


1.5 cc. 


4th 50 cc. 


1.0 cc. 


5th 50 cc. 


0,5 cc. 



In this case the free ammonia would be .0020, and the albuminoid 
ammonia .0206 parts per 100,000. 

The compounds produced by action of ammonia on mercuric so- 
lutions are considered as substitutions of iHg for 2 H in NH4 and are 
called mercur-ammoniums. Tetra-mercur-ammonium iodide (NHgj I) 
is a brown precipitate soluble in excess of KI in presence of KOH 
with a brown yellow color, proportionate to the amount of NH3. 

NH3 -f (2Hgl2 -f 2KI + 3KOH) = NHg.I -f sKI + 3H2O. 



If practicable, a determination of the total nitrogen in the organic 
matter should be carried on at the same time by the Kjeldahl process. 
(See page 7.) 

NITRITES. 

As soon as the foregoing determinations are well started the test 
for the second product of decay, the nitrites, is made. Waters of 
Class I must be freed from color by milk of alumina, and filtered through 



filters washed with nitrite-free water. loo cc, of the colorless water are 
treated in special tubes with three reagents, added in the following order 
and quantities : i cc. HCl i : 4, 2 cc. sulphanilic acid, 2 cc, naphthylamine 
hydrochlorate. The filtration and determination should be carried on 
within the half hour, since the air of any room in which gas is burned 
contains nitrites. 

The pink color of the azo a amidonaphthylic parabenzolsulphonic 
acid, 

N N H 



c 


c c 


/ ^ 


/ \ / w 


H — C C 


H — C C C — H 


II 1 


1 1 1 


H — C C 


H— C C C— H 


\ // 


^ / \ ^ 


c 


c c 


/ 


1 1 


S03H 


NH2 H 



which is formed when nitrites are present, is compared with that of 
known amounts of standard nitrite solution, containing .0000001 gram 
N in I cc. Sewage effluents and waters from bad wells often need 
to be diluted, 10 cc, or even i cc, being made up to 100 cc. before 
adding the reagents. 

* 

NITRATES. 

Nitrogen in the third stage, that of nitrates, is next determined. 
In case of colorless well waters, i cc. and 2 cc. are measured out 
with a capillary pipette into 2|-inch porcelain dishes and set away 
to evaporate spontaneously in a place free from dust. For surface 
waters, always low in nitrates, 10 cc. are taken from the decolorized 
portion filtered for nitrites, and the dishes are placed on the top of the 
water bath until the bulk is reduced to about 2 cc, when they are set 
away to evaporate spontaneously. 

This determination depends on the color given by an ammoniacal 
solution of trinitrophenol (picric acid), which in this case is formed 
by the action of the nitrates contained in the cold, dry residue upon 
the phenol-disulphonic acid with which it is moistened. Six or eight 
drops of the acid are run directly upon the residue and carefully rubbed 
into it with a short glass rod to insure complete contact of the acid 
and the residue in the dish. After a moment or two 7 cc. of water 
are added, and 3 cc. of an alkali (preferably ammonia), to distinct 
alkaline reaction. 



The yellow color thus produced is compared with standards, i cc. 
•oooooi gram N, in the same way as in the two previous tests.' 

HO HO 

I I 

C C 

/ ^ / \ 

H — C C— SO3H NO2 — C C— NO2 

II I +3 HNO3 = II I + 2 H2SO4 

H — C C — H H — C C — H 

\ -^ \ ^ 

C C + H2O 

I I 

S03H N02 

phenol- disulphonic acid. picric acid. 



KJELDAHL PROCESS FOR TOTAL ORGANIC NITROGEN. 

Five hundred cc. of the water are poured into a round-bottomed 
flask, of about 900 cc. capacity, and boiled until 200 cc. have been 
distilled off. The free ammonia which is thus expelled may, if desired, 
be determined by connecting the flask with a condenser. To the 
water remaining in the flask is added, after cooling, 10 cc. of pure 
concentrated sulphuric acid. After mixing, the flask is placed in an 
inclined position on wire gauze, on a ring-stand or other convenient 
support, and boiled cautiously, until all the water is driven off and the 
concentrated sulphuric acid is white or a very pale yellow. After cool- 
ing, 200 cc. of water free from ammonia are added, the neck of the 
flask being washed free from acid, and then 100 cc. of sodium hydrate 
solution. The flask is immediately connected with the condenser and 
then shaken to mix the contents. 

The distillation at the start is conducted rather slowly. After the 
first 50 cc. are condensed, the contents of the flask may be boiled more 
rapidly until 150 cc. to 175 cc. have altogether been collected. The 
total distillate is made up to 250 cc. with water free from ammonia, well 
mixed, and 50 cc. taken for nesslerization. 

The sulphuric acid oxidizes the carbon of the organic matter, 
thus liberating the nitrogen in the form of NHg which remains as 
(NH4)2SOi until released by distillation with NaOH. 

The Kjeldahl process is very much simpler as applied to waters 
than it is for many organic substances — flour, for instance. The organic 



'References: Sprengel, Pogg. Ann. 121, p. 188; Grandval and Lajoux, Compt. 
Rend. loi, p. 62; Fox, Tech. Quar. i, p. i ; Hazen & Clark, Jour. Anal. & App. Chem. 
5, p. I, Gill, Jour. Am. Chem. Soc. 16, 122. 



8 

matter in surface waters can be easily oxidized by sulphuric acid with- 
out the aid of potassium permanganate or mercury. 

CARBONACEOUS MATTER, OR " OXYGEN CONSUMED." 

KubeVs Hot Acid Method. 

loo cc. (or 25 cc. of very highly colored waters) are measured into 
a 250 cc. flask. 8 cc. of H2SO4 (i : 3), and 10 to 20 cc. of standardized, 
approximately — permanganate added, the whole boiled for five minutes 
and cooled one minute. The color is then discharged by 10 cc. of ex- 
actly — oxalic acid and the solution titrated with the permanganate 
to a faint permanent pink. Since i cc. of the oxalic acid corresponds 
to .00008 gram oxygen, the number of cubic centimeters of perman- 
ganate which have been used to oxidize the organic matter must be 
multiplied by its value referred to the oxalic acid as a standard. 

Example. 11 cc. permanganate solution are decolorized by 10 cc. 
oxalic acid; i cc. of permanganate has, therefore, a value of .000072 
gram oxygen. 

100 cc. of the sample of water-]- 10 cc. oxalic acid required 14 cc. 
permanganate. 

14 cc. — II cc. = 3 cc. X .000072 =: .0002 16 oxygen ; or expressed 
in parts per 100,000 — .2160.. 

CHLORINE, 

Colored surface waters are treated with milk of alumina to remove 
the color as follows: About 750 cc. are poured, without measuring, into 
a flask holding at least one liter, 3 to 5 cc. of the alumina added, and 
the water brought to the boiling point. The flask is now set aside in 
an inclined position so that the alumina may settle out and allow of the 
decantation of two measured portions of 250 cc. each, which are con- 
centrated in six-inch evaporating dishes on the steam bath to 25 cc. 
A clean feather, moistened with distilled water, is used to rub the sides 
of the dish and loosen any adhering residue. Three drops of a neutral 
solution of potassium chromate are added, and the solution titrated (in 
the same evaporating dish in which it was evaporated) with silver 
nitrate, with or without the addition of sodium chloride. The latter 
solution has always a strength of 0.00 1 gram CI in i cc. The sil- 
ver nitrate is usually one half the value. Colorless waters of Classes II 
and III do not need to be treated with milk of alumina. If high in 
chlorine, 25 cc. may be titrated directly; if low in chlorine, 250 cc. are 
concentrated as above. 



RESIDUE ON EVAPORATION. 

A portion of the water to be examined (200 cc. of waters of Class I, 
100 cc. of waters of Classes II and III) is evaporated in a weighed plat- 
inum dish on a water bath. After drying in an oven at ioo°C. for two 
or three hours, the dish is left in the desiccator over sulphuric acid for 
some hours. 

This gives the total weight of inorganic matter contained in the 
water, and in case of the waters of Class I of the organic matter as 
well. This latter may be burned off in the radiator, leaving "fixed 
solids " or mineral matter. 

HARDNESS. 

The amount of soap solution required to give a foam or lather with 
50 cc. of water, which remains five minutes after shaking in a 250 cc. 
bottle, is read from the burette, and the corresponding quantity of cal- 
cium carbonate (or other salts) is taken from the table given in Sutton's 
Volumetric Analysis, page 370. 

DISSOLVED OXYGEN. 

Witikler' s'' Method. 

When water is taken from a faucet, a glass-stoppered bottle of 
known capacity, holding from 50 to 250 cubic centimeters, is filled by 
means of a tube which passes to the bottom of the bottle. A con- 
siderable amount of water is allowed to pass through the bottle and 
overflow at the top. In taking samples from streams or ponds a stop- 
per with two holes is used. A tube passing through one of these holes 
is sunk in the water to the desired depth, and the other is connected 
with a larger bottle of at least four times the capacity of the smaller 
one and fitted in the same way. From the larger bottle the air is 
exhausted by the lungs or by an air pump until it is nearly filled with 
water. Unless the determination is to be made at once the rubber 
stopper in the smaller bottle is quickly replaced by the glass stopper, 
so that no air is left in the bottle. 

In making the determinations a small amount of a saturated solu- 
tion of manganous sulphate is added with a pipette having a long 
capillary point reaching below the surface of the water, and in the 
same way a concentrated solution of potassium iodide and sodium 
hydrate. The glass stopper is now inserted, leaving no bubble of 



' Berichte der deutsch. chem. Gesell., Vol. XXI, p. 2843. 



10 

air, and the contents well mixed. Strong hydrochloric acid is added, 
after most of the precipitate has settled to the bottom of the bottle. 
The contents of the bottle are now poured into a flask or other con- 
venient vessel, and the liberated iodine (in amount proportional to the 
amount of dissolved oxygen in the water) is titrated with thiosulphate. 

In calculating the amount of oxygen, a correction must be made for 
the volume of the reagents used, which should not be more than i per 
cent of the total volume. If the precipitate had settled before the 
acid was added no allowance should be made for the amount of acid, 
since the water it displaces contains no oxygen or iodine. If water 
is collected in the ordinary way and transferred to the apparatus by 
pouring, there will inevitably be an absorption of oxygen, unless the 
water is already saturated. Thus a process which gives excellent results 
when the water is nearly or quite saturated may fail entirely to give 
accurate results when the dissolved oxygen is low or absent. 

The results are reported in " percentage of saturation," the amount 
of oxygen which water will take up at the observed temperature being 
used as a basis. Winkler has calculated these amounts from o° to 30°.' 
It frequently happens that percentages greater than one hundred are 
obtained, due to the supersaturation of the water with oxygen.^ 

Determinations of dissolved oxygen in ponds and streams are best 
made on the spot. The very simple apparatus required for the Winkler 
process can be packed in small space, and the entire determination 
requires only a few minutes. The absorption of the oxygen by the 
manganous hydrate is complete almost at once, and it is unnecessary 
to allow it to settle for a long time before adding acid. The titration 
can be made with a small burette or pipette with accurate results. 

The temperature of the water at the depth from which the sample 
is taken is conveniently determined by means of a thermometer fitted 
by a doubly-perforated stopper to a bottle of about 500 cc. capacity, 
which has been filled with some of the Water and then lowered to the 
desired depth. 

IRON. 

Treat the residue on evaporation of 200 cc. of water with about 
5 cc. of HCl (strong acid diluted with an equal bulk of water) on a 
water bath, being careful to carry the acid nearly to the edge of the 
dish to insure its contact with all the residue. When the residue is 



' Berichte, Vol. XXII, p. 1772. 

* Technology Quarterly, Vol. V, p. 250. 



II 

completely dissolved (with the exception of silica), the solution is rinsed 
with a loo cc. tube and diluted to about 50 cc. A solution of perman- 
ganate is added drop by drop until the liquid remains pink for at least 
ten minutes. 

After the pink color has faded 15 cc. of a solution of potassium 
sulphocyanate (5 grams to the liter) is added, and after twenty minutes 
the color is read, using standards made up at the same time from a 
solution of which i cc. contains 0,000 1 gram of iron. 

The greatest care is necessary to prevent access of dust and to 
exclude any possible contamination ; also to avoid loss of ferric chloride 
by overheating, and in ignited residues to secure the complete solution 
of the iron. 

The results, with due precaution, have been very satisfactory.' 

ODOR. 

The odor of waters is obtained by shaking violently the sample 
in one of the large collecting bottles when it is about one half full, then 
removing the stopper and quickly putting the nose to the mouth of the 
bottle. An odor can often be detected in this way which would be en- 
tirely inappreciable if the water were poured into a tumbler. The odor 
which is given off when a water is heated is sometimes the same as the 
odor of the water when cold, sometimes it is different. The hot odor 
is obtained by heating on an iron plate about 200 cc. of the water in a 
beaker of 500 cc. capacity covered with a watch glass. The water is 
quickly heated until the air bubbles have all been driven off and the 
water is about to boil. The beaker is then taken off the plate, and, after 
cooling for about five minutes, it is shaken by a rotary movement, the 
watch glass removed, and the nose put inside the beaker. It is only for 
an instant, as a rule, that an odor can be perceived. 

COLOR. 

Most of the surface waters of the State have a yellowish-brown 
color more or less pronounced. The tint corresponds, particularly in 
the lower grades, very closely to that of nesslerized ammonia, so that 
the standards for reading ammonia can be used also for the deter- 
mination of the color. The comparison is made in the same kind of 
50 cc. tubes that are used for the ammonia determinations, but the 
tubes used for this purpose are kept separate from those used for the 
ammonia, since the least amount of alkali remaining in a tube (if im- 



' Thomson, Journ. Chem. Soc, Vol. XLVII, p. 493, 1885. 



12 

perfectly washed) alters the color of the water. The scale used corre- 
sponds with the amount in the standards. Thus a color of i.o is that 
corresponding to the nesslerization of i cc. of the standard ammonium 
chloride solution ; o.i is the color produced with o.i cc. of this solution. 
In the higher grades of color, over i. the tint varies considerably from 
the nesslerized ammonia, and the degree of color is then better deter- 
mined in wider tubes and in less depth. Standards made from very 
dark water from cedar swamps by various degrees of dilution, and veri- 
fied by direct comparison with nesslerized ammonia, are also used. 

TURBIDITY AND SEDIMENT. 

The suspended matter remaining in the water after it has rested 
quietly in the collecting bottle for twelve hours or more is called its 
turbidity, and that which has settled to the bottom of the bottle its 
sediment. 

Good ground waters are often entirely free from turbidity and sedi- 
ment, but surface waters are seldom free from suspended matter. The 
turbidity is very various in character and amount, sometimes milky from 
clay, but more generally it consists of fine pollen- like particles. These 
are generally living algae or infusoria, and a practiced eye can, not in- 
frequently, recognize their forms. Some of the lower animal forms can 
also be seen by the naked eye, and the larger Entomostraca are quite 
noticeable in many waters. 

The sediment may be earthy or flocculent, in the latter case it is 
generally dkbris of organic matter of various kinds. The degree of tur- 
bidity is expressed by the terms " very slight," " slight," " distinct," and 
" decided," and the degree of sediment by " very slight," " slight," 
"considerable," and "heavy." 

REAGENTS. 

Nessler Reagent. — Dissolve 61.750 grams KI in 250 cc. distilled 
water. Add 415 cc. of a cold solution of HgCl2 which has been satu- 
rated by boiling an excess of the salt and allowing it to crystallize out. 
Dissolve the slight precipitate of Hglj by adding 0.750 gram powdered 
KI. Then add 300 grams of KOH dissolved in 250 cc. of water. 
Make up to the liter and allow it to stand over night to settle. This 
solution should give the required color with ammonia within five min- 
utes, and should not precipitate within two hours. 

Alkaline Permanganate. — Dissolve 400 grams of refined potassium 
carbonate in 2 liters of distilled water and heat to boiling in a silver 



13 

dish. After removing the lamp add 250 grams of quicklime of the best 
quality piece by piece. When all the lime is slaked, heat to boiling 
again, and transfer to a large bottle or crock which can be tightly 
closed to exclude the air. Allow it to settle over night, siphon off 
the clear liquid, and add water uiftil the sp. gr. = 1.125. One liter of 
this caustic potash and 8 grams of permanganate crystals are boiled for 
thirty minutes, the water lost on evaporation being replaced. When 
the chemicals used are all good there should be no correction needed 
for ammonia in this solution. 

Standard Nitrite Solution. — The pure silver nitrite used in making 
this solution is prepared by the double decomposition of silver nitrate 
and potassium nitrite and repeated crystallizations from water of the 
rather insoluble silver nitrite, i.i grams of this silver nitrite are 
dissolved in water nitrite-free, the silver completely precipitated by 
the addition of the standard salt solution used in the determination of 
chlorine, and the solution made up to one liter. 100 cc. of this strong 
solution are diluted to i liter, and 10 cc. of this last solution again 
diluted to i liter. The final solution is the one used in preparing 
standards, i cc. = .0000001 gram of nitrogen. 

Sulphanilic Acid. — Dissolve 8 grams (Kahlbaum's) in i liter of 
water. This is a saturated solution. 

NaphthylatJiine Hydrochlorate. — Dissolve 8 grams in 992 cc. of 
water and add 8 cc. strong HCl. (Keep in the dark.) 

Standard Nitrate Solution. — 0.720 gram of pure KNO3 is dis- 
solved in I liter of water. Of this strong solution 10 cc. are diluted 
to I liter. I cc. of this dilute solution corresponds to .000001 gram 
nitrogen. 

Phenol- Disulphonic Acid. — Heat together 3 grams synthetic phenol 
with 37 grams pure concentrated H2SO4 on a boiling water bath for six 
hours. 

Sodium Hydrate. — For Kjeldahl process. Dissolve 200 grams good 
quality caustic soda in i liter of water. Boil with 3 grams of permanga- 
nate crystals to free the solution from nitrogen. 

Sulphuric Acid. — For Kjeldahl process. This should be free from 
nitrogen. May be obtained from Baker & Adamson, Easton, Penn. 

Calcium Chloride and Soap Solutio?is. — For hardness. Dissolve 
0.200 gram of pure Iceland spar in dilute HCl, and evaporate several 
times to remove excess of acid. Dissolve the calcium chloride thus 
formed in i liter of water. Dissolve 100 grams best dry white Castile 
soap in 80 per cent alcohol. From this strong solution make a weaker 
solution (about 100 cc. to a liter of 70 per cent alcohol) of such a 



14 

strength that 14.25 cc. will give the required lather with 50 cc. of the 
above CaCL solution. 

Reagefits for Wmkkr's Process. — 360 grams of NaOH and 100 
grams of KI in i liter of water. 

48 grams of MnSOi -}- 4H2O in i liter of water. HCl sp. gr, 
1-125. 

Thiosulphate y^ -f- 4 grams ammonia carbonate. Dilute to ^$0 
for use. Standardize by potassium bichromate. 



The following books will be found on the laboratory shelves for consultation 
as to methods of analysis and interpretation of the results obtained : 

Wanklyn — Water Analysis. 
Frankland — Water Analysis. 
Nichols — Water Supply. 

State Board of Health Reports for Massachusetts. 
" " " " " Michigan. 

" ' " " " " " Illinois. 

National Board of Health Report for 1882. 
Tiemann-Gaertner — Untersuchung des Wassers. 
Fischer — Die Chemische Technologie des Wassers. 

The following papers on special topics relating to water supply and water analysis 
will be found in the reports of the Massachusetts State Board of Health, the Pro- 
ceedings of the Society of Arts, and the Technology Quarterly. They are also avail- 
able in pamphlet form : 

The Chemical Examination of Water. 

The Interpretation of Water Analyses. 

Chemical Examination of Drinking Water. 

Discussion of Special Topics relating to the Quality of Public Water Supplies. 

The Analysis of Water — Chemical, Microscopical, and Bacteriological. 

On the Determination of the Organic Nitrogen in Natural Waters by the Kjeldahl 
Method. 

On the Amount of Dissolved Oxygen contained in Waters of Ponds and Reservoirs 
at Different Depths. 

On the Amount of Dissolved Oxygen contained in the Waters of Ponds and Reser- 
voirs at Different Depths in Winter, under the Ice. 

The Odor and Color of Surface Waters. 

The Effect of the Aeration of Natural Waters. 

The Filtration of Natural Waters. 

On the Mineral Contents of Some Natural Waters in Massachusetts. 

The Purification of Water by Freezing. 



